Instrument dial illumination



Aug. 30, 1938. c. 'r. WALLIS 2,123,339

INSTRUMENT DIAL ILLUMINATION Filed March 26, 1936 Patented Aug. 30, 1,938

INSTRUDIENT DIAL ILLUMHVATION Cyril T. Wallis, Rochester, N. Y assignor to Generai Motors Corporation, Detroit, Mich, a cor.-

poration -of Delaware Application March 26, i936, Serial No. 71,002

1 Claim. (Cl. 240-:8.16)

This invention relates generally to the illumination of instrument dials, and more particularly to the uniform illumination of the dials of the various instruments usually provided on the in- 5 strument panel of automobiles.

In the usual internally lighted instrument panel it has been the recent practice to use several sources of light, and attempt to locate the various instruments with reference thereto so that there will be a substantially uniform illumination of the dials of the various instruments.

The use of several sources of light has improved the light distribution over that formerly obtained with only a single light source, but it has been found that invariably some instrument dials are lighted to a greater degree than others. This may be explained by the fact that to obtain a substantially even illumination of all portions of the respective dials, it is necessary to 0 provide larger light admitting apertures in the larger instruments than in the smaller instruments and as a consequence thereof, the larger dials will be illuminated to a greater degree of intensity than the smaller dials.

While it might be possible to obtain more uniform illumination to some extent by positioning the different instruments so that their distance from the light source varies in accordance with the sizes of the light admitting apertures that may be required for proper lighting of each dial,

it is proposed to avoid this rather impractical expedient by my invention.

The object of my invention is, therefore, to provide a simple and inexpensive means for obtaining the uniform illumination of the various instruments regardless of their respective locations with reference to the light source and the relative sizes of their light admitting apertures, by reducing the intensity of the light admitted to those instruments which would otherwise be illuminated to a greater degree than other instruments.

It is a further object to accomplish this reduction in intensity with reference to only those 5 instruments where this is necessary without diffusing the light or changing the color thereof.

Specifically, my invention consists in the use of windows in the light admitting apertures of the instruments which may be of pyralin or some similar suitable material and blocking or preventing the light from passing through portions of such windows. This may be accomplished in various ways such as inking a portion of the surface of the window, and a preferred method consists in printing directly on the windows half-tone similar to that used for newspaper work.

In the drawing: Fig. l-is a front elevation of an instrument panel, partly in section. v

' Fig. 2 is an enlarged fragmentary section taken on line 2-2 of Fig. 1.

Fig. 3 is a perspective of one of the instrument windows.

Fig. 4 is an enlarged perspective of a portion of one of the instrument windows.

' Referring to Fig. 1, there is shown an instrument panel I of conventional construction to which are suitably secured a number of instruments which may consist of a centrally located speedometer 2 with its dial 3, an ammeter and oil gauge with respective dials 4 and 5 at the right of the speedometer, and a gasoline gauge and temperature indicator with respective dials 6 and I at the left of the speedometer.

The ammeter and oil gauge are contained within a unitary housing '8 and the gasoline gauge and temperature indicator are similarly contained within a single housing. Both of these housings are provided on the sides toward the light sources, indicated generally at 9, with apertures covered by windows, such as at III, of translucent or transparent material. mg l I of the speedometer is likewise provided with apertures on the sides toward the light sources with windows such as at l2. Only the right side of the speedometer housing with its aperture and window is shown in section but it will be understood that the left side of the speedometer housing is similarly formed to admit light from the light source on that side of the speedometer.

Each light source may take the form of a conventional incandescent lamp l3 which may be fastened in any suitable manner to the rear of the instrument panel by means which permits the projection of light from the lamp through the windows onto the dials of the instruments.

In the general arrangement of instruments shown in the drawing, it will be noted that the dial of the centrally located speedometer is illuminated by both light sources whereas the dials of the instruments at either side of the speedometer are illuminated by only a single light source. As a consequence of this relative location of the instruments with reference to the light sources and the necessity for providing for the illumination of the speedometer dial through windows on both sides to obtain more uniform illumination of all portions of this dial, it will be apparent that the dial of the speedometer would ordinarily The housbe illuminated to a greater degree of intensity than the other dials.

To remedy this condition, namely, where the intensity of the light on the speedometer dial is greater than that on the dials of other instruments, it is proposed to reduce or cut down the intensity of the light on the speedometer dial, and a simple and inexpensive means of accomplishing this has been found to consist-in preventing light from passing through portions of the speedometer windows. As noted heretofore, the actual location and size of the windows must be predetermined to provide for substantially even illumination of all portions of the speedometer dial so that it is impossible to reduce the size of the windows without seriously aiiecting the light distribution on the dial.

Although it is contemplated that the window, which is generally of pyralin or some similar; material, may be treated in various ways to prevent light from passing through portions thereof the preferred method consists in inking portions of the window surface and more specifically in printing a half-tone, similar to that used for newspaper work and commercial printing, directly on one surface of the window.

Generally, this particular method, as applied in the present instance, would consist in placing a mesh screen on the window material and, with an inked roller or the like, supplying ink which would pass through the holes in the screen and onto the surface of the window material, thereby producing a multiplicity of inked or opaque spots on the window material such as shown at I 4 in Fig. 4. v

This method is not only simple and inexpensive but may be used to obtain any desired degree of illumination by choosing a certain size of screen in making the half-tone. Since screens used in commercial printing are available in varying sizes ranging from 55 to 150 holes per square inch, it will be apparent that it is possible to obtain practically any degree of light transmission through the window that may be required in any predetermined condition belotv the normal intensity of light on any dial.

Although this invention is shown in' the drawing with reference to a conventional arrangement of the various instruments in which it is only necessary to cut down the intensity of'the light on the speedometer dial, it should be understood that the inventionmay be used with any other arrangement of instruments where the intensity of light on one or more dials would otherwise be greater than on the other dial or dials, and different degrees of light transmission might be provided with windows of diflerent instruments in the same panel in order to obtain a uniform degree of illumination on all instruments.

Also there may be instances in which some aisasso portions of the same dial maybe illuminated to different degrees in which it might be possible to obtain more even distribution of light over the entire dial by printing a half-tone on only a portion of the instrument window or using different size screens for printing diflerent portions of the window.

As stated heretofore, the reduction in intensity of the light passing through the instrument 'window is obtained without any diifusion or coloring of the light, but it should be understood that the window may, of course, be also colored, if desired, or have one surface frosted or otherwise treated to diffuse the light passing through the window for a more uniform illumination of the instrument dial.

Although described for the purpose of obtaining more uniform illumination of different instrument dials, it will be obvious that this invention may also be of use in instances where for some reason it is desired to illuminate diil'erent instrument dials with different intensities so that one dial would be more prominent than others.

In its broadest aspect, then, the invention resides in the provision of a light transmitting window which is rendered opaque to only the extent desired to obtain some predetermined degree of illumination of a lower intensity than would be the case with a transparent or translucent window, and in a simple and inexpensive method of reducing the intensity of the light passing through the window without diffusing or coloring the light.

The invention is, however, not to be limited in all respects to the preferred method of treating the instrument windows which has been described herein, and is obviously applicable to instruments and gauges of any type and panels for use on airplanes or other objects.

I claim:

The combination in an instrument panel, of a light source, a plurality of adjacent instruments with dials and casings therefor, apertures in said casings to admit light from said light source to illuminate said dials. said instruments being so constructed and associated with said light source that the light intensity on one of said instrument dials would ordinarily be greater than on another of said instrument dials, and means to reduce the light intensity on said one dial to provide substantially uniform intensity on said respective dials, which consists in the provision of a window of light transmitting material in the aperture of the instrument casing therefor on which material. is printed a half-tone with that size screen which has been found to permit the passage there through of only sufilcient light to obtain an'intensity on said one dial which is substantially th same as that on said other dial.

CYRIL T. WALLIS. 

